Production of diolefins



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' unsaturated materials Patented Jan. 13, 1948 Wilson D. Seyfried, Wooster, Standard lOil Development poration or Delaware Tex., asslgnor to Company, a cor- Application` May 18, 1944, Serial No. 536,209 6 Claims. (Cl. 260-680) Thel present invention is directed to a process for treating hydrocarbons to recover therefrom a.

fraction rich in unsaturated compounds of the character of diolens. In its more specific aspects, it is directed to a process wherein an olefin containing hydrocarbon feed stock is dehydrogenated to form diolens and in which the manipulative steps prevent the formation of peroxides in the hydrocarbon stream.

A process commonly used in the art for producing diolens of the character of butadiene includes the steps of subjecting a predominantly olenic feed stock to dehydrogenation conditions in a dehydrogenation reactorto form diolens as well as other unsaturated materials, such as acetylenes. The hydrocarbon stream from the dehydrogenation unit is quenched by being brought into intimate contact with a quench oil, and after this quenching step it is further cooled to condense a diolen-containing fraction which is removed to a, suitable stabilization zone. The step in the process of contacting the hydrocarbon fraction removed from the dehydrogenation reactor with a quench oil is essential for profitable commercial operations in order to terminate the reaction and prevent the conversion of diolelns into less desirable materials. The quenching step is necessarily carried out at relatively high temperatures, and if free oxygen is allowed to enter the quenching zone it will react with the present therein to form peroxides. Such peroxides are to be avoided because they not only are easily detonated, but in addition they catalyze the formation of high molecular weight polymers from the unsaturated hydrocarbons, such as diolefins and acetylenes, present in the hydrocarbon stream.

The product removed from the dehydrogenation zone does not have free oxygen present therein so the quenching zone may be operated withl present therein by the selecmoved from the quenching oil by the addition of a suitable antioxidant inhibitor to the quenching oil. It is usually desirable to supplement the addition of antioxidant inhibitors to the quenching oil with the storage .of oil under a blanket oi' inert gas and when such a storage method is used, the inhibitor serves initially to remove oxygen from the quenching oil and is also available in the oil in case the storage system allows oxygen-containing gases to come in contact with the oil after it has been initially treated.

The oxidation inhibitor to be employed may be 2 any of the commonly known oxidation inhibitors which are soluble in petroleum. A suitable inhibitor is isobutyl-p-amino phenol. hibitor may beemployed in amounts varying from about 0.05 to 0.50 lb. per 1,000 gals. of petroamounts maybe employed, but

A preferred cut of petroleum phenols heavy cracked distillates are also formed in Hot hydrocarbon I2 by line I3, hav- The vapors removed I4 are still at a relatively high temthe dehydrogenation reactor. product is removed from vessel ing cooler I4 present therein. from cooler temperature of the vapor below that at which substantial conversion of the diolens into other productswill take place. I'he quenched vapors are withdrawn from tower l5 through line I1 and This inabout 250-700 F. with 'of the major portion of subjected to cooling steps to cause cooling and condensation of the desired diolefln-containing product. In the drawing the hot vapors pass through line I1 into cooler I8 of the heatexchanger type and pass thence through line I9 into tower 20, where they are quenched by contact with water. Quenching water accumulating in the lower portion of the tower is recycled through line 2l containing pump 22 and cooling means 23 and retirned into the upper portion of the tower. The hot vapors iiow upwardly through tower 20 countercurrent to the iiow of the water therein and are removed vfrom the upper portion of the tower through line 24 and passed into a suitable means, such as drum 25, to separate entrained water from the hydrocarbon vapors. Separated water is removed from the lower portion of the drum through outlet 25. Hydrocarbon vapors are withdrawn from the upper portion of the drum through outlet 21 and are passed through compressor 23, cooler 29 and into a second drum 30. The compression and cooling steps to which the vapors are subjected causes the condensation the diolenn fraction. This desired fraction settles out in drum 30 and may be removed from the drum through outlet 3l and sent to a suitable stabilizing means, not shown. The uncondensed hydrocarbons in vessel 30 may have present therein minor portions of desirable dioleiins, and are passed from drum 30 through line 32 to absorber vessel 33. A heavyoil is introduced into an upper portion of tower 33 by line 34 and flows downwardly therein to dissolve diolens and other hydrocarbons from the upwardly iiowing vapor. The absorption oil with the desired constituents dissolved therein may be removed from the lower portion of the tower via line 35 and hydrocarbon gases and vapors are removed from the top of the tower by line 36 and discarded from the system.

High boiling oil suitable for use in the quenching zone I is introduced via inlet 40 and as it flows through this line a small amount of antioxidant inhibitor is added thereto by line 4 I The oil containing the inhibitor is discharged into storage tank 45. If desired, the surface of the oil in storage tank 45 may be allowed to come in contact with the atmosphere and the inhibitor in the oil relied upon to prevent the presence of free oxygen in the oil. Under such conditions, it is necessary to add additional antioxidant inhibitor from time to time to replace the inhibitor which is being continuously used up by coming in contact with the oxygen of the atmosphere. In the preferred operation, however, the initially inhibited oil is passed into storage tank 45 and there-4 upon blanketed with an oxygen-free gas. A suitable inert gas for this purpose is methane but other oxygen-free gases, such as ue gas or nitrogen, may also be used for this purpose. The inert gas may be stored in vessel 46 and removed therefrom to the upper portion of tank 45 by line 41 controlled by valve 48. As oil is needed for the quenching tower it is withdrawn from the tank through line 49 controlled by valve 50 and allowed to enter tower I5 via inlet I6.

The quenching oil accumulated at the bottom of tower I5 has dissolved therein small amounts of the hydrocarbon vapors. This accumulated quench oil is withdrawn from the tower through line 5I containing pump 52 and the stream split, with a portion being returned to the tower by line 53 and the remainder being passed through line 54 to a stripping tower 55 provided with heating means 55. vapors separated from the quenching removing product from the quenching zone oil in stripping tower 55 are returned to quenching tower I5 through line 51. The stripped quenching oil resulting from the stripping action in tower 55 is withdrawn from the bottom of the tower through line 34, passed through a cooler 58 and is then used as the lean absorbent oil in absorption tower 33. The rich absorption oil'removed from tower 33 via line 35 is admixed with the oil owing in line 53 and the mixture returned to quenching tower I5.

As a specic example of the preparation of a quench oil, a Coastal gas oil having an initial boiling point of 590 F., a iinal boiling point of F. a viscosity at 100 F. of '77.9 Saybolt seconds. and a gravity of 25.7 A. P. I., had added thereto isobutyl-p-amino phenol as an inhibitor in amounts of 0.25 pound of inhibitor per 1000 gallons of oil. This inhibited oil was then stored under a blanket oi methane in a storage tank and a quench oil was withdrawn therefrom as desired for quenching the hot vapors removed from a dehydrogenation reactor. The substitution of this inhibited quench oil with no free oxygen present therein for the quench oil previously employed resulted in a substantial reduction in the polymers formed in the hydrocarbon stream and reduced substantially the fouling of the equipment. As another speciiic example, a raiilnate having an initial boiling point of 590 F. and a nal boiling point of '120 F. and inhibited in the same manner has been employed as a quench oil with similar satisfactory results.

The temperatures of the dehydrogenation reaction and the suitable quenching range for reducing the temperatures of the gaseous product removed from the dehydrogenation reactor are well known to the art and are described, for example, in detail in U. S. patent application Serial No. 510,204, filed in the name of Carl E. Kleiber et al. on November 13, 1943, now Patent No. 2,414,817. As a typical example, it may be stated that the hydrocarbon vapors removed from the dehydrogenation reactor may have a temperature in the range of 1150 to 1300" F., that the cooler I4, which may conveniently be a waste heat boiler, may serve to reduce the temperature of the hydrocarbon vapors to a temperature ranging from 500 F. to 600 F., and the quenching step conducted in vessel I5 may be operated to reduce the temperature of the vaporous hydrocarbons to within the range of 200 F. to 250 F. It is to be understood that these conditions are given by Way 0f example only. and are not intended as limitation of the process.

Having fully described and illustrated the practice of the present invention, what I desire to claim is:

1. In a process for producing diolei'lns comprising the steps of passing lan olefin-containing hydrocarbon feed stock through a dehydrogenation zone maintained under conditions to convert olefin to diolen and in which product is removed from the dehydrogenation zone and passed to a quenching zone, the step of cooling the product in to a temperature substantially above atmospheric by bringing it into intimate contact with a mineral oil containing free oxygen and having an oxidation inhibitor added thereto.

2. In a process for producing diolens including the steps of passing an olefin-containing hydrocarbon feed stock into a dehydrogenation zone and maintaining it in said zone under conditions to cause the production of dioleiin and acetylene,

the dehydrogenation Y amena zone to a quenching zone, removing product from the quenching zone, further cooling to condense at least a portion of the product, separating the condensed product and passing the uncondensed product into an absorption zone, the steps of contacting the product in the quenching zone with a mineral oil containing free oxygen and having an oxidation inhibitor present therein to cool said product to a temperature substantially above atmospheric and the step of contacting the uncondensed hydrocarbons in the absorption zone with a mineral oil having an oxidation inhibitor added thereto.

3. In a process for producing diolens from a hydrocarbon feed stock comprising oleflns by passing the feed stock through a dehydrogenation zone to convert at least a portion of the feed stock into diolefn and acetylene, passing the product from the dehydrogenation zone into a quenching zone to reduce its temperature to a temperature substantially above atmospheric, removing hydrocarbon vapors from the quenching zone, cooling said vapors to condense a portion thereof, separating the condensed portion from the uncondensed portion, and passing the uncondensed portion through an absorption zone, the steps o1' adding an oxidation inhibitor to a heavy hydrocarbon oil containing free oxygen and employing the oil containing the inhibitor as the quenching oil in the quenching zone and as the absorption 30 Vvcoil in the absorption zone.

4. A method in accordance with claim 3 in which the inhibitor is a phenol of petroleum origin.

5. A method in accordance with claim 3 in 35 6 which the heavy hydrocarbon oil is a naphthenic ses oil and in which the oxidation inhibitor is a phenol o1' petroleum o 6. A method in accordance with claim 3 in which the heavy hydrocarbon oil is a petroleum ramnate and in which the oxidation inhibitor is a phenol of petroleum origin.

- WILSON D. SEYFRIED. v

REFEBEN CES CITED The following refere file of this patent:

UNITED STATES PATENTS Number Name Date 2,313,531 Figg, Jr., et al. Mar. 9, 1943 2,339,560 de Simo et al Jan. 18, 1944 2,209,215 Wiezevich et al. July 23,-1940 2,322,122 Frohiich et al. June 15, 1943 2,091,375 Pyzel Aug. 31, 1937 2,228,028 Brower Jan. 7, 1941 2,378,067 Dorsett et al. June 12, 1945 2,257,078 Soday Sept. 23, 1941 2,388,041 Craig Oct. 30, 1945 2,384,645 Schulze Sept. 11, 1945 FOREIGN PATENTS Number Country Date 463.244 Great Britain Mar. 24, 1937 OTHER. REFERENCES Scott, Jour. Ind. Eng. Chem.

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